First of all: this is a remix of https://www.thingiverse.com/thing:1319128 and all the credits goes to the original designer.
I used the original feet for almost a year now and they work great. But for an upgrade i needed more room at the under-frame of my Kossel, and the original thing can't go beyond the corner-mounting pieces of the Kossel. This one does because it uses two sides of the aluminum frame instead of three.
It is a tight fit and you need some force, but this remix doesn't fall off when you move your printer.
Happy Dampening :)
Use 5 or 6 perimeters. Of course this model does not use that number of walls, but it gives a strong and solid piece without useless infill.